The NAS went offline. After forcing the device back online, the user could not find the shared folder holding his data.
He tried to recover the data using File Scavenger® but most recover files did not retain the original name and could not be opened.

Diagnosis:

For a RAID 1 (mirrored set) either of the drive could be used for data recovery.

The drive contained four partitions. The largest partition hosted an ext4 volume holding the user data.